Downhole seal

ABSTRACT

A downhole seal comprises a seal body having a swellable material configured to swell upon exposure to a swelling activator to establish a seal within a wellbore, and at least one protection element configured to protect at least a portion of the seal body when the downhole seal is translated within a wellbore. The protection element defines a reaming element configured to ream a portion of the wellbore while the downhole seal is translated therethrough.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority from Great Britain Application No.0906746.3, filed Apr. 20, 2009 incorporated by reference in itsentirety.

BACKGROUND

The present invention relates to a downhole seal, and in particular, butnot exclusively, to a downhole seal incorporating a swellable materialand a reaming element configured to ream an internal surface of thewellbore.

Swelling seals for use in a downhole environment in the oil and gasindustry are well known. These seals have numerous applications, such asfor zonal isolation purposes, to facilitate compartmentalized fracingoperations, to provide cement assurance and the like. Typically, a bandof a swellable material is mounted on the outer surface of a tubularbody, such as liner, production tubing etc. which is then run into awellbore to a required depth, where exposure to a suitable swellingactivator, such as oil or water, causes the swellable material to swell.This swelling is used to provide an annular seal between the tubularbody and a wall of the wellbore—such a sealing arrangement isconventionally defined in the art as a packer.

Swelling seals of the type described above may be run into an openwellbore, such that the swelling seals are tripped through a bore withexposed rock. The drilling operation used to form the bore may produce avery coarse wall surface and may present regions of reduced diameter.There is therefore a risk that the swelling seals could be damaged byengagement with the rock of the open bore during transit therethrough.

Swelling seals may also be run through a tubing string, such as a casingstring, liner string or the like. Tubing strings are often cemented inplace within a drilled bore, which is achieved by pumping a cementslurry downward through the tubing string and then upward into anannulus formed between the tubing string and the wall of the drilledbore. It is possible for cement residue to adhere and cure on theinternal wall of the tubing string. Such adhered cement may present abarrier to the passage of a swelling seal, and may potentially be asource of damage to the seal.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided adownhole seal comprising:

a seal body comprising a swellable material configured to swell uponexposure to a swelling activator to establish a seal within a wellbore;and

at least one reaming element configured to ream an internal surface of awellbore.

The reaming element may be configured to ream an internal surface of thewellbore while the downhole seal is being translated therein.Accordingly, translating the downhole seal, for example to reach arequired location, may also permit a reaming operation within thewellbore to be achieved. This reaming operation may be utilised forcleaning purposes, improving the consistency of the bore diameter or thelike.

The reaming element may be configured to ream a wall surface of adrilled bore. This may facilitate cleaning of the wellbore, creation ofa uniform diameter of the wellbore or the like. For example, a wellboreformed by drilling may have a relatively uneven and course wall surface,which surface may be addressed by use of the reaming element of thedownhole seal.

The reaming element may be configured to ream an internal wall surfaceof a tubing string. This may facilitate cleaning of the tubing string.For example, the reaming element may be configured to remove depositsfrom the tubing wall surface, such as deposits of cement which mayremain adhered to the tubing wall surface following a cementingoperation. Other deposits may include salts, tars and the like. Thereaming element may also function as a wiper.

At least one reaming element may be configured to protect at least aportion of the seal body when the downhole seal is translated within awellbore. In use, the downhole seal may be translated through awellbore, for example to locate the seal at a desired location, whereinat least one reaming element provides protection to the seal body. Forexample, the reaming element may assist to prevent or minimise contactof the seal body with a wall surface of the wellbore, a blockage withinthe wellbore or the like. Once the swellable material is exposed to aswelling activator, the seal body will swell to establish a seal withinthe wellbore.

The seal body may be configured to swell from an unswollen configurationto a swollen configuration to establish a seal.

At least one reaming element may define an outer dimension which isgreater than an outer dimension of the seal body when in an unswollenconfiguration. In this arrangement at least one reaming element mayprevent or minimise contact of the seal body, when in its unswollenconfiguration, with a wall surface of a wellbore. This mayadvantageously provide protection for the seal body while in aconfiguration when translation through a wellbore is achievable ordesirable.

At least one reaming element may define an outer dimension which isequal to or less than an outer dimension of the seal body when in aswollen configuration. This arrangement may assist to prevent or atleast minimise the reaming element from interfering with theestablishment of a seal by swelling of the seal body.

The outer dimension of at least one of the reaming element and the sealbody may define an outer diameter.

The downhole seal may be configured to be mounted on a base member. Thebase member may comprise a downhole tubular, such as a casing tubular,liner tubular, production tubular or the like. The base member may formpart of the downhole seal of the present invention.

The seal body may be configured to be mounted on the base member. Theseal body may be configured to be mounted on an outer surface of thebase member. The seal body may be configured to be mounted on an axialend portion of the base member. The seal body may be directly mounted onthe base member, for example by being bonded thereto. The seal body maybe indirectly mounted on the base member. For example, the seal body maybe mounted on a sleeve configured to be mounted on the base member.

At least one reaming element may be mounted on the base member. At leastone reaming element may be directly mounted on the base member. At leastone reaming element may be integrally formed with the base member. Atleast one reaming element may be separately formed and directly securedto the base member.

At least one reaming element may be indirectly mounted on the basemember. For example, the reaming element may be mounted on a sleeveconfigured to be mounted on the base member. At least one reamingelement may be integrally formed with the sleeve.

In one embodiment at least one reaming element may be mounted on asleeve, wherein the sleeve may be configured to be located on a basemember independently from the seal body.

The downhole seal may comprise a common sleeve configured to supportboth the seal body and at least one reaming element. In this arrangementboth the seal body and at least one reaming element may be mounted on abase member in a single operation.

At least one reaming element may be provided separately of the sealbody. For example, at least one reaming element may be formed separatelyand mounted adjacent or in the region of the seal body.

At least one reaming element may be located adjacent an axial end of theseal body. At least one reaming element may be located intermediateaxial ends of the seal body. At least one reaming element may be locatedon or within the seal body. At least one reaming element may be at leastpartially embedded within the seal body. At least one reaming elementmay at least partially extend through the seal body.

The downhole seal may be configured to be located within a wellboredefined by an a open drilled bore. The downhole seal may be configuredto be located within a wellbore defined by a tubing string, such as apipeline, casing string, liner string or the like.

A plurality of reaming elements may be provided.

At least one reaming element may be defined by a rib structure.

At least one reaming element may comprise a relatively hard material,such as tungsten carbide.

At least one reaming element may be generally spiral shaped. Thisarrangement may permit at least one reaming element to extend bothcircumferentially and axially.

At least one reaming element may be generally annular.

At least a portion of the downhole seal may be configured for rotation.

At least one reaming element may define a centraliser element configuredto centralise the seal body within a wellbore.

The downhole seal may comprise at least one protection elementconfigured to protect at least a portion of the seal body when thedownhole seal is translated within a wellbore. At least one protectionelement may be configured to define a reaming element. Features definedabove associated with at least one reaming element may apply to at leastone protection element.

As defined above, the swellable material is configured to swell uponexposure to an activator. The activator may comprise a chemicalactivator, thermodynamic activator, electromagnetic activator,mechanical activator or the like. In embodiments of the presentinvention the swellable material may be configured to swell uponexposure to a material present within a wellbore. The material maycomprise water, oil, gas or the like. The material may comprise anartificial material delivered into the wellbore, such as cement,drilling mud or the like. The material may comprise a naturallyoccurring material, such as water or hydrocarbons produced from asubterranean reservoir.

The downhole seal may be configured to function as a packer.

According to a second aspect of the present invention there is provideda method of establishing a seal within a wellbore, comprising:

providing a downhole seal having a seal body and a reaming element;

translating the downhole seal through a wellbore and reaming a portionof the wellbore with the reaming element; and

exposing the swellable material to an activator to cause the seal bodyto swell to establish a seal.

The reaming element may also function protect the seal body fromengagement with a wall surface of the wellbore.

The downhole seal may be provided in accordance with the first aspect.Defined features and stated and implied methods of use of the downholeseal according to the first aspect apply to the method according to thesecond aspect.

According to a third aspect of the present invention there is provided adownhole tool comprising:

a seal body comprising a swellable material configured to swell uponexposure to a swelling activator to establish a seal within a wellbore:and

at least one reaming element configured to ream an internal surface of awellbore.

The reaming element may be configured to ream an internal surface of thewellbore while the downhole tool is being translated therein.Accordingly, translating the downhole tool, for example to reach arequired location at which to establish a seal, will also permit areaming operation within the wellbore to be achieved. This reamingoperation may be utilised for cleaning purposes, improving theconsistency of the bore diameter or the like.

The reaming element may be configured to ream a wall surface of adrilled bore. The reaming element may be configured to ream an internalwall surface of a tubing string.

The downhole tool according to the third aspect may share features ofthe downhole seal according to the first aspect.

According to a fourth aspect of the present invention there is provideda method of reaming a wellbore, comprising:

providing a downhole tool comprising:

a seal body comprising a swellable material configured to swell uponexposure to a swelling activator to establish a seal within a wellbore;and

at least one reaming element; and

translating the downhole tool through a wellbore to ream the wellborewith the at least one reaming element.

The method may comprise establishing a seal within the wellbore usingthe seal body.

According to a fifth aspect of the present invention there is provided amethod of manufacturing a downhole seal, comprising:

mounting a seal body comprising a swellable material on a base member;and

mounting a reaming element on the base member.

According to a sixth aspect of the present invention there is provided adownhole seal comprising:

a seal body comprising a swellable material configured to swell uponexposure to a swelling activator to establish a seal within a wellbore;and

at least one protection element configured to protect at least a portionof the seal body when the downhole seal is translated within a wellbore,wherein at least one protection element defines a reaming elementconfigured to ream an internal surface of a wellbore.

According to a seventh aspect of the present invention there is provideda method of establishing a seal within a wellbore, comprising:

providing a downhole seal having a seal body and a protecting element,wherein the seal body comprises a swellable material;

translating the downhole seal through a wellbore, wherein the protectionelement protects the seal body;

reaming a portion of the wellbore with the protection element; and

exposing the swellable material to an activator to cause the seal bodyto swell to establish a seal.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described,by way of example only, with reference to the accompanying drawings, inwhich:

FIG. 1 is a diagrammatic representation of a downhole seal in accordancewith one embodiment of the present invention;

FIG. 2 is cross-sectional view of the downhole seal of FIG. 1, whereinthe left side of FIG. 2 represents the seal in a run-in configuration,and the right side of FIG. 2 represents the seal in a sealedconfiguration;

FIG. 3 is a diagrammatic representation of a downhole seal in accordancewith an alternative embodiment of the present invention;

FIG. 4 is a cross-sectional view of a possible configuration ofprotection elements of the downhole seal of FIG. 3, wherein the leftside of FIG. 4 represents the seal in a run-in configuration, and theright side of FIG. 4 represents the seal in a sealed configuration;

FIG. 5 is a cross-sectional view of another possible configuration ofprotection elements of the downhole seal of FIG. 3, wherein the leftside of FIG. 5 represents the seal in a run-in configuration, and theright side of FIG. 5 represents the seal in a sealed configuration; and

FIG. 6 is a diagrammatic representation of a downhole seal in accordancewith a further embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

A downhole seal, generally identified by reference numeral 10, accordingto an embodiment of the present invention is shown in FIG. 1. As will bedescribed in further detail below, the downhole seal 10 is configured toprovide a seal within a wellbore, in addition to perform a reamingoperation within the wellbore. Accordingly, the downhole seal 10 mayequally be defined as a downhole tool.

The downhole seal 10 is mounted on a tubular body 12 forming part of atubing string. In the example disclosed the tubular body includes aliner tubular. The seal 10 includes a seal body 14 which comprises aswellable material configured to swell upon exposure to a swellingactivator, such as oil or water. The seal 10 further includes a pair ofsleeves or collars 16 disposed on the tubular body 12 at axiallyopposite ends of the seal body 14, wherein the sleeves 16 are secured tothe tubular body 12 via a number of screws 18.

Each sleeve 16 carries a plurality of spiral reaming elements 20, whichas will be described in detail below are used in the present exemplaryembodiment to protect the seal body 14 and to function to ream aninternal wall surface of a wellbore.

Reference is now made to FIG. 2 in which the downhole seal 10 is shown,in cross-section, in use within a wellbore 22. In the embodiment shownthe wellbore 22 is an open drilled bore. For convenience and brevity,the left side of FIG. 2 shows the seal 10 in a run-in configuration, andthe right side of FIG. 2 shows the seal 10 in a sealing configuration.

The reaming elements 20 describe an outer diameter which is greater thanthat of the seal body when in an unswollen configuration, as shown inthe left side of FIG. 2. Accordingly, the reaming elements 20 functionto prevent the seal body 14 from contacting the wall 24 of the wellbore22, and thus assist to minimise damage to the seal body 14 while beingtranslated through the wellbore 22.

Additionally, it is often the case that a drilling operation produces abore with a very course or uneven wall surface, which may include borerestrictions 26, for example. Such bore restrictions 26 are undesirablefor many reasons, which may include obstructing the passage of an objecttherethrough, damaging a passing object, preventing uniform circulationof cement, and preventing coaxial alignment of tubing, for example,within the wellbore. Translation of the seal 10 through the wellbore 22will effect reaming of the bore wall 24 which will assist to remove borerestrictions 26 and provide a more even bore wall surface 24. It shouldbe noted that the reaming operation may be assisted by rotating thetubular member 12, with torque transmitted to the sleeves 16 through thescrews 18.

Once the seal 10 is located at the required depth within the bore 22,exposure of the swellable material to a swelling activator will causethe seal body 14 to swell and establish a seal within an annulus 28defined between the tubular body 12 and the wall 24 of the wellbore 22,as demonstrated in the right hand side of FIG. 2.

The sleeves 16 may function as anti-extrusion rings, for example wheresignificant swelling pressure is present, or where a significantpressure differential is present across the established seal. That is,the sleeves 16 may assist to prevent extrusion of the seal body 14 alongthe annulus 28 due to elevated pressures and/or pressure differentials.

Reference is now made to FIG. 3 in which there is shown a downhole seal,generally identified by reference numeral 40, in accordance with analternative embodiment of the present invention. The downhole seal 40 ismounted on a tubular body 42 and includes a seal body 44 which comprisesa swellable material. A plurality of spiral reaming elements 46 aredisposed within the seal body 46, which, similar to reaming elements 12in the embodiment first shown in FIG. 1, function to ream a wall surfaceof a wellbore, while protecting the seal body 44 from damage.

The reaming elements 46 may be disposed within the seal body 46 in anumber of configurations. Two such exemplary configurations aredescribed below, with reference to FIGS. 4 and 5. These configurationsare described with reference to downhole seals, shown in cross-sectionin FIGS. 4 and 5, and identified by respective reference numerals 40 aand 40 b. The downhole seals 40 a, 40 b are shown in use within adrilled wellbore 52.

Referring first to FIG. 4, the downhole seal 40 a with reaming elements46 a arranged in accordance with a first configuration will bedescribed. It should be noted that for convenience and brevity the seal40 a is shown in a run-in configuration in the left hand side of FIG. 4,and in a sealing configuration in the right hand side of FIG. 4.

The reaming elements 46 a are embedded and supported within the sealbody 44 a so as to protrude therefrom when the seal body 44 a is in anunswollen configuration, as shown in the left side of FIG. 4. Theprotruding reaming elements 46 a may therefore prevent the seal body 44a from engaging the wall surface 54 of the wellbore 52, and also effectreaming of the bore wall 54 when the seal 40 a is translated through thewellbore 52.

Once the downhole seal 40 a is located at the required depth within thewellbore 52 the seal body 44 a may swell upon exposure to a swellingactivator to establish a seal within the annulus 58 defined between thetubular body 42 a and the bore wall 54, as shown in the right side ofFIG. 4. As shown in FIG. 4, the seal body 44 a envelops the reamingelements 46 a when the seal body 44 a is swollen.

Referring now to FIG. 5, the downhole seal 40 b with reaming elements 46b arranged in accordance with a second configuration will be described.It should be noted that for convenience and brevity the seal 40 b isshown in a run-in configuration in the left hand side of FIG. 5, and ina sealing configuration in the right hand side of FIG. 5.

The reaming elements 46 b are formed integrally with a sleeve 60 whichis mounted on and secured to the tubular body 42 b. The seal body 44 bis mounted on the outer surface of the sleeve 60 and the reamingelements 46 b extend radially outwardly from the sleeve 60 and throughthe seal body 44 b. The reaming elements 46 b protrude from the outersurface of the seal body 44 b when the seal body 44 b is in an unswollenstate, as shown in the left side of FIG. 5. The protruding reamingelements 46 b may therefore prevent the seal body 44 b from engaging thewall surface 54 of the wellbore 52, and also effect reaming of the borewall 54 when the seal 40 b is translated through the wellbore 52.

Once the downhole seal 40 b is located at the required depth within thewellbore 52 the seal body 44 b may swell upon exposure to a swellingactivator to establish a seal within the annulus 58 defined between thetubular body 42 b and the bore wall 54, as shown in the right side ofFIG. 5. As shown in FIG. 5, the seal body 44 b envelops the reamingelements 46 b when the seal body 44 b is swollen

In the embodiments described above the downhole seal is mounted on atubular body forming part of a tubing string. This tubular body may beany downhole tubular, such as a tubular around 9.14 m (30 feet) long. Itmay not be desirable, however, to provide a seal on such a tubinglength, as this may present supply problems, handling problems, increasecosts and the like. Referring to FIG. 6, a downhole seal, generallyidentified by reference numeral 70, according to an embodiment of thepresent invention may be mounted on and form part of a pup-joint tubular72, which are known in the art, and typically have a length of around0.91 m (3 feet), although other lengths are possible. The pup-jointtubular 72 comprises connectors 74 at either end thereof, permittingconnection within a larger tubing string. Suitable connectors 74 arewell known in the art, and may include threaded connectors. Theprovision of a downhole seal 70 in combination with a pup-joint tubular72 may permit flexibility of the present invention to be incorporated,relatively easily, within a tubing string being run into a wellbore.

It should be understood that the embodiments described herein are merelyexemplary and that various modifications may be made thereto withoutdeparting from the scope of the present invention. For example, reamingelements may be provided both separately of the seal body, as shown inFIG. 1, and also as part or embedded within the seal body, as shown inFIG. 3. Additionally, the reaming elements may be provided in anyconfiguration, and for example may not be spiral shaped. For example,the reaming elements may be generally annular. Furthermore, the reamingelements may alternatively, or additionally function to centralise thedownhole seal within a wellbore.

In the embodiments described above the downhole seals are shown in usewithin an open drilled bore. However, the downhole seal of the presentinvention has application within a tubing string, such as a pipeline,casing string, liner string, production string or the like. In suchexamples the reaming elements may be configured to remove deposits, suchas cement, salts and the like, formed on the internal surface of thetubing string.

Additionally, a plurality of downhole seals may be provided incombination along the length of a tubular or tubing string.

1. A downhole seal comprising: a seal body comprising a swellablematerial configured to swell upon exposure to a swelling activator toestablish a seal within a wellbore; and at least one reaming elementconfigured to ream an internal surface of a wellbore.
 2. The downholeseal according to claim 1, wherein at least one reaming element isconfigured to ream an internal surface of a wellbore while the downholeseal is being translated therein.
 3. The downhole seal according toclaim 1, wherein at least one reaming element is configured to ream awall surface of at least one of a drilled bore and an internal wallsurface of a tubing string.
 4. The downhole seal according to claim 1,wherein at least one reaming element defines an outer dimension which isgreater than an outer dimension of the seal body when in an unswollenconfiguration.
 5. The downhole seal according to claim 1, wherein atleast one reaming element defines an outer dimension which is equal toor less than an outer dimension of the seal body when in a swollenconfiguration.
 6. The downhole seal according to claim 1, configured tobe mounted on a base member.
 7. The downhole seal according to claim 1,wherein at least one reaming element is mounted on a sleeve.
 8. Thedownhole seal according to claim 1, wherein at least one reaming elementis mounted on a sleeve, wherein the sleeve is configured to be locatedon a base member independently from the seal body.
 9. The downhole sealaccording to claim 1, comprising a common sleeve configured to supportboth the seal body and at least one reaming element.
 10. The downholeseal according to claim 1, wherein at least one reaming element isprovided separately of the seal body.
 11. The downhole seal according toclaim 1, wherein at least one reaming element is located adjacent anaxial end of the seal body.
 12. The downhole seal according to claim 1,wherein at least one reaming element is located intermediate axial endsof the seal body.
 13. The downhole seal according to claim 1, wherein atleast one reaming element is located on or within the seal body.
 14. Thedownhole seal according to claim 1, wherein at least one reaming elementis at least partially embedded within the seal body.
 15. The downholeseal according to claim 1, wherein at least one reaming element at leastpartially extends through the seal body.
 16. The downhole seal accordingto claim 1, configured to be located within a wellbore defined by atleast one of an a open drilled bore and a wellbore defined by a tubingstring.
 17. The downhole seal according to claim 1, comprising aplurality of reaming elements.
 18. The downhole seal according to claim1, wherein at least one reaming element is defined by a rib structure.19. The downhole seal according to claim 1, wherein at least one reamingelement is rigid.
 20. The downhole seal according to claim 1, wherein atleast one reaming element is generally spiral shaped.
 21. The downholeseal according to claim 1, wherein at least one reaming element isgenerally annular.
 22. The downhole seal according to claim 1, whereinat least a portion of the downhole seal is configured for rotation. 23.The downhole seal according to claim 1, wherein at least one reamingelement defines a centraliser element configured to centralise the sealbody within a wellbore.
 24. The downhole seal according to claim 1,wherein the reaming element is configured to protect at least a portionof the seal body when the downhole seal is translated within a wellbore.25. The downhole seal according to claim 1, comprising a protectionelement configured to protect at least a portion of the seal body whenthe downhole seal is translated within a wellbore.
 26. The downhole sealaccording to claim 25, wherein the protection element defines at leastone reaming element.
 27. A method of establishing a seal within awellbore, comprising: providing a downhole seal having a seal body and areaming element; translating the downhole seal through a wellbore andreaming a portion of the wellbore with the reaming element; and exposingthe swellable material to an activator to cause the seal body to swellto establish a seal.
 28. A method of reaming a wellbore, comprising:providing a downhole tool comprising: a seal body comprising a swellablematerial configured to swell upon exposure to a swelling activator toestablish a seal within a wellbore; and at least one reaming element;and translating the downhole tool through a wellbore to ream thewellbore with the at least one reaming element.
 29. A downhole sealcomprising: a seal body comprising a swellable material configured toswell upon exposure to a swelling activator to establish a seal within awellbore; and at least one protection element configured to protect atleast a portion of the seal body when the downhole seal is translatedwithin a wellbore, wherein the protection element defines a reamingelement configured to ream an internal surface of a wellbore.
 30. Amethod of establishing a seal within a wellbore, comprising: providing adownhole seal having a seal body and a protecting element, wherein theseal body comprises a swellable material; translating the downhole sealthrough a wellbore, wherein the protection element protects the sealbody; reaming a portion of the wellbore with the protection element; andexposing the swellable material to an activator to cause the seal bodyto swell to establish a seal.